Sheaffer's slim rollerball refill in medium point and black ink. The slim format is the correct one for the VFM, 100, 300, Agio, Intensity, Sagaris, Taranis, Valor and Prelude Signature - the fatter Classic refill will not fit these pens, so it is worth checking which of the two your pen takes before ordering.
A genuine Sheaffer part, matched to the flow the pen was built around.
